Construction system

ABSTRACT

A reinforcing structure is described for use in supporting a floor at a junction thereof with a structural column. The structure has several generally elongate, preassembled frame structures, each frame structure are disposed in rows parallel to one another. The frame structures incorporate the main top and bottom reinforcement bars for the reinforced floor with integral shear connectors forming part of the frame structures and the shear connectors tying the top and bottom reinforcement together. Transverse internal reinforcing bars are disposed parallel to one another and connected across the top or bottom reinforcing bars of each frame structure to connect the preassembled frame structures into a cagework of spaced-apart, rigidly connected frame structures.

PRIORITY

This application is a National Phase Application of PCT/EP2010/055569 filed Apr. 26, 2010, which claims priority to Irish Patent Application No. S2009/0325, filed Apr. 24, 2009, and Irish Patent Application No. S2010/0101, filed Feb. 25, 2010, the disclosures of which are incorporated herein by reference in their entireties.

FIELD OF THE INVENTION

This invention relates to a construction system, in particular to the construction of floors which are supported by building columns. The invention is particularly concerned with reinforced floors of the poured type.

BACKGROUND OF THE INVENTION

It is known to provide pre-fabricated elements for use in the construction industry, for example pre-fabricated floor slabs, walls, etc. Such pre-fabricated slabs may be provided at a construction site, which may then be arranged in position on site as required. Once positioned, wet concrete can be poured on or around the pre-fabricated slab to hold it in position, and to allow for finishing of the construction stage.

The use of pre-fabricated components allows for a proportion of the work required for construction to be completed in advance off-site. This provides a reduction in the amount of formwork, shuttering and scaffolding required during construction projects. As a result, this has the advantage of reducing the on-site construction time, and streamlining the construction process through the use of pre-defined components. In addition, the pre-fabricated construction system may be tested in advance in a laboratory environment to provide for appropriate safety certification, etc.

One of the disadvantages of using pre-fabricated construction components however, is that substantial additional work must be carried out to ensure that the pre-fabricated system is reinforced adequately within the finished structure. At locations where the effects experienced by various stresses and strains are most pronounced, e.g. at the interface between a supporting column and a transverse pre-fabricated ceiling/floor slab, it is vitally important that such reinforcement is configured to withstand predicted stresses and strains. Examples of reinforcements used include providing supporting trusses, either partially within the pre-cast slab, or added to the pre-cast slab after manufacture, i.e. on-site. Examples of known reinforced pre-cast slabs can be seen in U.S. Pat. No. 5,448,866; U.S. Pat. No. 3,283,466; U.S. Pat. No. 3,763,613; U.S. Pat. No. 3,930,348; and U.S. Pat. No. 4,050,213. However, such reinforcements (particularly where reinforcement is applied to the pre-cast slab after manufacture) may be of a reduced quality, e.g. incorrectly-placed welds, inadequate use of reinforcement members provided.

Furthermore, there is a need to provide an integrated construction system that takes account of the pre-cast components used in its construction, to provide for improved reinforcement and resistance to applied loads. Examples of known integrated construction systems can be seen in U.S. Pat. No. 915,421; and U.S. Pat. No. 4,505,087.

Therefore, there is a need to provide a pre-fabricated construction system having an integrated reinforcement system that addresses any one or several of the above problems. It would also be advantageous to provide a construction system having an optimum construction scheme.

Another aspect of reinforced floor construction is concerned with the forces which the floor is required to withstand, in particular around column supports. Such floors which are supported on a building column have to handle three major force components: compressive, tensile and shear forces. Concrete and other analogous building materials are usually chosen because they have inherently high compressive strength. Horizontal reinforcement, usually of steel, provides tensile reinforcement, while vertical reinforcement members provides shear reinforcement.

In the area around the column, all of the forces on the floor are greatest, with failure most likely to occur through “punching shear”, in which the weight of the floor causes the concrete to fail in a zone around the column, which punches through the floor as the floor collapses around the failure zone. FIG. 22 shows a cut-away section through a floor 80 and column 82 indicating the characteristic shear pattern observed around a column as an inverted frusto-conical failure zone 84.

Several punching shear reinforcement solutions are known and used. A review of these systems can be found in the article “Proprietary punching shear reinforcement systems”, Andrew Pratt, Concrete, May 2002, pages 34-37. These include links such as those described in British Standard 4466:1989 as shapes 85 and 77, which are respectively L- and square U-shaped members whose free top ends are bent into an inverted J-shaped hook. In the L-shaped member, the upper hook end is hooked over a reinforcing bar forming part of the top layer reinforcement and the lower 90 degree bend is pushed under the bottom bar and tied into place. In the U-shaped variant, the bottom of the square U-shape is tied to a pair of bars forming part of the bottom layer of reinforcement, before the top steel is fixed in place inside the upper hook ends. Such links are difficult and time-consuming to fix and difficult to check for correct fixing afterwards.

An alternative solution is the stud rail formed from a series of studs affixed to a non-structural horizontal rail. The studs are formed of reinforcing steel with an enlarged head at one or both ends for connection to the rail. The stud rails are positioned within the main reinforcement but do not form part of it. Typically stud rails are installed after the main reinforcement is in place and can be difficult to install if the reinforcement is congested. They also suffer the disadvantage of possibly becoming dislodged when the concrete is poured onto the reinforcement and formwork.

Shear ladders are formed of a series of vertical shear links (such as the BS 4466:1989 shape 85 described above) welded to three horizontal anchor bars to form an elongated “chair”. These chairs are placed crosswise on the B1 layer of reinforcement and support the top layers of reinforcement, with the vertical members providing shear reinforcement within the concrete.

Other known solutions include shear band strips, stirrup mats, shearhoops, shear stirrups and shearheads all of which can be difficult and time consuming to install onsite due to the need to integrate them when placing the reinforcement.

It is thus a further object of this invention to provide an alternative structural system for reinforcing a floor at a junction with a structural column.

SUMMARY OF THE INVENTION

In one aspect, the invention provides a reinforcing structure for use in supporting a floor at a junction thereof with a structural column, comprising:

-   -   a plurality of generally elongate, preassembled frame         structures, each frame structure having a major longitudinal         axis, said frame structures being disposed in rows with their         major longitudinal axes parallel to one another, and each frame         structure comprising:         -   at least one first reinforcing bar disposed parallel to the             major longitudinal axis of said frame structure;         -   at least one second reinforcing bar disposed parallel to the             major longitudinal axis of said frame structure;         -   a plurality of shear connectors disposed at spaced intervals             along the longitudinal axis of the frame structure, each             shear connector comprising a reinforcing member extending             between a first reinforcing bar and a second reinforcing             bar, the reinforcing member being shaped to extend around             the first and second reinforcing bars such that they are             tied together by the reinforcing member;     -   a plurality of transverse internal reinforcing bars disposed         parallel to one another and connected across the first or second         reinforcing bars of each frame structure to connect the         preassembled frame structures into a cagework of spaced-apart,         rigidly connected frame structures.

Preferably, the reinforcing member comprises a top portion, a bottom portion, and a bridging portion between the top and bottom portions, the bridging portion extending between the first and second reinforcing bars, and the top and bottom portions each extending in a direction transverse to the first and second reinforcing bars to contain the first and second reinforcing bars.

Preferably, the bridging portion and at least a part of the top and bottom portions together define an elongated C shaped section of the shear connector.

Further preferably, the shear connector is in the form of a hoop which includes a pair of said bridging portions, said top portion and said bottom portion.

Preferably, said at least one first reinforcing bar comprises a first pair of reinforcing bars disposed parallel to one another and to said major longitudinal axis, and spaced apart from one another along the direction of the transverse internal reinforcing bars to provide a pair of top edges of the frame structure.

Preferably, said at least one second reinforcing bar comprises a second pair of reinforcing bars disposed parallel to one another and to said major longitudinal axis, and spaced apart from one another along the direction of the transverse internal reinforcing bars to provide a pair of bottom edges of the frame structure.

In this configuration, the frame structures have a pair of top bars and a pair of bottom bars, each connected and enclosed by the hoop member. It is particularly preferred that this structure has an elongated cuboid frame shape.

Accordingly, it is preferred that each shear connector comprises a generally rectangular hoop having four interior corners with a respective one of each of said first and second pairs of reinforcing bars connected to the hoop at a respective interior corner thereof.

Such a cagework provides an easily assembled structure which can simply be positioned to integrate all of the main components of reinforcement needed around a column. The advantage of this is that the construction of the reinforcement, which is usually part of the critical path for erecting a building, is greatly accelerated due to the use of either a pre-assembled cagework or a cagework which can be assembled onsite from pre-assembled frame structures welded together with the transverse top reinforcing bars.

Preferably, said shear connectors are spaced along each frame structure such that their two dimensional arrangement across said cagework provides a zone of shear reinforcement, whereby when said reinforcing structure is mounted on a structural column to support a reinforced floor, said zone of shear reinforcement coincides with the region in which punching reinforcement is required between the column and the floor.

The reinforcing structure preferably further comprises two sets of said transverse internal reinforcing bars, namely a set of top transverse internal reinforcing bars connected to the underside of the first reinforcing bars and a set of bottom transverse internal reinforcing bars connected to the top side of the second reinforcing bars, whereby the first reinforcing bars are sandwiched between the top transverse internal reinforcing bars and a top portion of the shear connectors and the second reinforcing bars are sandwiched between the bottom transverse internal reinforcing bars and a bottom portion of the shear connectors.

The bottom transverse internal reinforcing bars may be replaced, if desired, by bottom transverse external reinforcing bars which are connected to the underside of the second reinforcing bars.

The reinforcing structure preferably further comprises a first set of extended reinforcing bars which extend horizontally beyond the perimeter of said cagework as defined by the frame structures, the first set of extended reinforcing bars disposed in a direction parallel to the first reinforcing bars of the frame structures.

In alternative embodiments, at least some of the first reinforcing bars and the top transverse internal reinforcing bars extend beyond the perimeter of the cagework as defined by the other components of the frame members.

Preferably, the cagework has a maximum extent in one direction which is not more than a maximum permitted dimension to for unrestricted transportation.

More preferably, the cagework has a maximum extent of 2.3-2.7 meters in one direction, more preferably about 2.5 meters.

Preferably, the dimensions of the cagework extend sufficiently far from the column support point to encompass the contraflexure points of a floor in which the cagework is situated, where the column support point forms part of a 7.5 m column grid.

Most preferably, the cagework has a lateral dimension greater than the distance between opposed contraflexure points on opposite sides of a column in a 7.5 m column grid floor, and less than the maximum dimension which can be transported by road without “wide load” restrictions being imposed on a carrying vehicle.

The reinforcing structure preferably further comprises a second set of extended reinforcing bars which extend horizontally beyond the perimeter of said cagework as defined by the frame structures, the second set of extended reinforcing bars disposed in a direction parallel to the transverse internal reinforcing bars.

Preferably, the first set of extended reinforcing bars are disposed on top of the top transverse internal reinforcing bars in the plane of the first reinforcing bars.

Further, preferably, the first set of extended reinforcing bars are spaced apart from the first reinforcing bars on the outside of the shear connectors.

Preferably the second set of extended reinforcing bars are disposed on top of the first reinforcing bars of the frame structures.

Further, preferably, where a set of top transverse internal reinforcing bars and said second set of extended reinforcing bars are provided, one or more of the top transverse internal reinforcing bars coincide with one or more of the second set of internal reinforcing bars when viewed from above the reinforcing structure.

There is also provided a method of constructing a reinforced floor, comprising the steps of:

-   -   mounting a reinforcing structure as defined above on a         structural support column such that the cagework sits         horizontally;     -   providing extended reinforcing bars which extend horizontally         beyond the perimeter of said cagework as defined by the frame         structures;     -   pouring a solidifying structural substance in a layer which         captures said reinforcing structure, whereby said solidifying         structural substance solidifies to form a reinforced floor.

Preferably, the step of mounting a reinforcing structure comprises providing said plurality of frame structures and said plurality of transverse top reinforcing bars, and constructing said reinforcing structure in situ on said column by connecting said frame structures and said reinforcing bars to one another and to said column to provide said cagework.

In an alternative method, the step of mounting a reinforcing structure comprises providing said reinforcing structure as a pre-assembled cagework, and mounting said cagework to said column.

There is also provided a method of constructing a reinforced floor, comprising the steps of:

-   -   providing a reinforcing structure as defined above;     -   pouring a solidifying structural substance in a layer which         captures said reinforcing structure, whereby said solidifying         structural substance solidifies to form a reinforced floor slab;     -   mounting said reinforced floor slab on a structural support         column such that the cagework sits horizontally;     -   building a reinforced floor outwardly from said mounted         reinforced floor slab either by pouring a floor around         reinforcing bars extending from said reinforced floor slab or by         connecting additional floor slabs to said mounted reinforced         floor slab.

Preferably, the step of pouring a solidifying structural substance in a layer results in said layer having a depth which captures the bottom edges and a portion of the shear connectors of each frame structure, leaving the top edges exposed, whereby extended reinforcing bars may be mounted to the exposed top portions of the frame structures to provide extended reinforcement to the floor beyond the floor slab.

There is also provided a reinforced floor comprising a reinforcing structure as defined above, mounted on a structural support column, and having extended reinforcing bars extending therefrom beyond the perimeter of said cagework as defined by the frame structures, and further comprising a solid structural material in a layer which surrounds and contains said reinforcing structure and said extended reinforcing bars.

In another aspect of the invention, there is provided a construction system comprising a plurality of pre-cast slabs, said pre-cast slabs including a plurality of column slabs, a plurality of inter-column slabs, and at least one bridging slab, wherein:

-   -   each column slab comprises a pre-cast column slab body having         upper and lower faces, said pre-cast column slab body having a         first network of reinforcing members embedded therein, a         plurality of first arch members extending above the upper         surface, said first arch members being interlinked with said         first network and thereby anchored within said pre-cast column         slab body, and a second network of reinforcing members disposed         above said pre-cast column slab body and being supported by and         connected to said plurality of first arch members;     -   each inter-column slab comprises a pre-cast inter-column slab         body having upper and lower faces and being positioned in         abutting relationship against one or more of said column slabs         along first adjoining edges, said pre-cast inter-column slab         body having one or more second arch members embedded in said         pre-cast inter-column slab body in proximity to said first         adjoining edges; and     -   the or each bridging slab comprises a pre-cast bridging slab         body having upper and lower faces and being shaped to complement         and abut against one or more of said inter-column slabs along         second adjoining edges, said pre-cast bridging slab body having         one or more third arch members embedded in said pre-cast         bridging slab body in proximity to said second adjoining edges.

The second network of reinforcing members provided at the column slabs, and supported by the first arch members, presents a table surface to receive a further network of reinforcing members. The utilisation of three layers of networks of reinforcing members at the location of the column slabs provides enhanced reinforcement in the vicinity of the column slab. As the column slabs are generally provided at those locations where the majority of the stresses and strains in construction can be found, e.g. at the interface between a floor and the supporting structural column, the construction system provides an effective used of reinforcement, as the reinforcing members are concentrated at the locations of importance. It will be understood that the dimensions of the slabs, as well as the dimensions of the arch members and the reinforcing members, may be chosen to provide adequate reinforcement of the construction system. Such an arrangement of components provides for a securely reinforced system, minimising the effects of deflection throughout the construction.

Preferably, said system further comprises at least one further network of reinforcing members, wherein said at least one further network of reinforcing members is positioned above said column slab, and wherein said at least one further network of reinforcing members received by said second network of reinforcing members and said plurality of first arch members.

Preferably, said second arch members are provided substantially perpendicular to said first adjoining edges.

Preferably, said third arch members are provided substantially parallel to said second adjoining edges.

Preferably, said first arch members are provided as the upper portion of a hoop, the lower portion being interlinked with said first network

Preferably, said second arch members are double arches, each arch being the upper portion of a respective hoop, the hoops being angled towards one another and being connected at their top ends.

Preferably, said third arch members are provided as a plurality of aligned, parallel arches, the arches being the upper portions of a continuous square-wave shaped member whose lower portions are embedded in said slab body.

Preferably, said column slabs are of a greater thickness than the inter-column slabs and the at least one bridging slab.

Preferably, said column slab is adapted to be coupled to a structural column.

Preferably, said column slab comprises a through-going aperture defined in said main body, wherein said aperture is adapted to receive a portion of a structural column.

Preferably, said column slab further comprises at least one column reinforcing bar, the at least one column reinforcing bar provided partially within said main body such that a portion of the column reinforcing bar extends across the through-going aperture defined in the main body.

The column reinforcing bar is used to couple the column slab to a supporting structural column, preferably by tying said column reinforcing bar to a supporting rod extending from said column.

Preferably, said second arch members are provided such that that the central axis of the second arch members are parallel to the longitudinal axis of the main body of the inter-column slab.

Preferably, said third arch members are provided such that that the central axis of the third arch members are parallel to the longitudinal axis of the main body of the bridging slab.

There is also provided a pre-cast slab for use in a pre-cast construction system, the slab comprising:

-   -   a main body having an upper surface and a lower surface;     -   a first network of reinforcing bars disposed within said main         body;     -   a plurality of discrete hoop elements, the hoop elements in the         form of a closed loop, said hoop elements disposed partly within         said main body and partly projecting above the upper surface of         said main body, such that one or more of said first network of         reinforcing bars pass through said hoop elements; and     -   a second network of reinforcing bars located above said upper         surface of said main body, such that one or more of said second         network of reinforcing bars pass through said hoop elements.

The particular construction of the pre-cast slab provides a substantially reinforced slab that is particularly adapted to the stresses and strains that occur at the interface between a floor and a supporting structural column. The provision of discrete hoop elements distributed about the main body, and anchored to the first and second networks of reinforcing bars presents a particularly reinforced pre-cast slab that can be used during construction.

Preferably, said hoop elements are provided in said slab in a regular grid arrangement of spaced parallel rows of hoop elements.

Preferably, said hoop elements are substantially rectangular, such that a first end of said substantially rectangular hoop elements are provided within said main body and a second end of said substantially rectangular hoop elements project above the upper surface of said main body.

Preferably, said hoop elements are coupled to said first network of reinforcing bars at the corners of said first end of said hoop elements provided within said main body, and wherein said hoop elements are coupled to said second network of reinforcing bars at the corners of said second end of said hoop elements provided above said main body.

Preferably, a through-going aperture is defined in the main body, the aperture extending from said upper surface to said lower surface.

The aperture is provided to allow the slab to be aligned with a supporting column in a structure.

Preferably, the slab further comprises at least one column reinforcing bar, the at least one column reinforcing bar provided partially within said main body such that a portion of the column reinforcing bar extends across the through-going aperture defined in the main body.

The column reinforcing bar can be used to couple with structural steel running through a building support column.

Preferably, said through-going aperture is tapered, such that the aperture opening at said upper surface is of reduced size than the aperture opening at said lower surface.

The particular aperture construction allows the pre-cast slab to interlock with a supporting column after poured concrete has been allowed to set, providing a further degree of structural security.

There is further provided a pre-cast slab for use in a pre-cast construction system, the slab comprising:

-   -   a substantially rectangular main body having an upper surface         and a lower surface, the main body further having a pair of         opposed major ends and a pair of opposed minor ends;     -   a network of reinforcing bars disposed within said main body;         and     -   at least one coupling member comprising a reinforcing frame         having a crenellated side profile, wherein a lower portion of         said reinforcing frame is provided within said main body and an         upper portion of said reinforcing frame projects above the upper         surface of said main body, and wherein said coupling member is         interlaced with said network of reinforcing bars.

The crenellated, or square-wave, profile of the coupling member provides an anchor point for fixation which is securely retained within the body of the slab, as the member is interlaced with the reinforcing network provided within the slab body, resulting in an improved distribution of load.

Preferably, said at least one coupling member is provided such that the central axis of the member is parallel to the longitudinal axis of the main body of the slab.

As the coupling member runs along the longitudinal direction of the slab body, this allows for the optimum arrangement of reinforcement, as the network of reinforcing bars disposed within the main body are allowed to couple with the coupling member at right angles, such that the reinforcing effects are maximised. Furthermore, in a regular right-angled grid arrangement of the network of reinforcing bars, this results in the coupling member aligned in parallel with the longitudinal bars of the reinforcing network, which are in general the primary reinforcing elements of the slab. This improves the distribution of stresses throughout the slab.

Preferably, said reinforcing frame is provided as a plurality of aligned, parallel arches, the arches being the upper portions of a continuous square-wave shaped member whose lower portions are embedded in said main body.

Preferably, said at least one coupling member is provided towards each of said opposed major ends of said main body.

Preferably, at least one of said reinforcing bars of said network comprises a first hooked end, said first hooked end provided adjacent an edge of said main body.

As the hooked end of the reinforcing bar is provided towards the edge of the main body, this allows for support of full stress to the edge of the slab, thereby increasing transverse stiffness of the slab.

Preferably, said network of reinforcing bars is arranged such that said first hooked end projects across the centreline of said reinforcing frame.

Alternatively, the slab further comprises at least one reinforcing brace provided within the main body, the at least one brace comprising a member projecting across the centreline of said reinforcing frame, wherein the lower end of said reinforcing frame is provided at a greater depth from said upper surface of said main body than the depth of said reinforcing frame from said upper surface.

Preferably, said at least one reinforcing brace comprises a U-shaped member.

Preferably, said at least one reinforcing brace is arranged such that the free ends of said U-shaped member project across the centreline of said reinforcing frame.

Preferably, the slab comprises:

-   -   a coupling array provided towards each of said opposed minor         ends of said main body, the coupling array comprising at least         one coupling frame, a lower end of said coupling frame provided         within said main body and an upper end of said coupling frame         projecting above the upper surface of said main body, wherein         said coupling frame comprises a plurality of arch members         interlinked with said network and thereby anchored within said         pre-cast column slab body,

As the coupling array is provided so reinforcing bars are interlaced with the coupling frames, any load applied to the coupling frames is distributed throughout the network of bars, and the coupling frames are securely held within the body of the slab.

Preferably, said arch members are double arches, each arch being the upper portion of a respective hoop, the hoops being angled towards one another and being connected at their top ends.

Preferably, said coupling array comprises a plurality of coupling frames, and wherein said inter-column slab further comprises at least one reinforcing element provided above the upper surface of the main body, the reinforcing element coupled to the top ends of said arch members in a coupling array.

Preferably, said coupling array is provided such that the central axis of the array is parallel to the longitudinal axis of the main body of the slab.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

FIG. 1 is an isometric view of a first pre-cast slab according to the invention;

FIG. 2 is a top plan view of the slab of FIG. 1;

FIG. 3 is a cross-sectional view of the slab of FIG. 1;

FIGS. 4-6 illustrate the steps involved in installing the slab of FIG. 1 in position on a construction site;

FIG. 7 is a first enlarged view of a portion of FIG. 6;

FIG. 8 is a second enlarged view of a portion of FIG. 6;

FIG. 9 is an isometric view of a second pre-cast slab according to the invention;

FIG. 10 is a front plan view of the slab of FIG. 9;

FIG. 11 is a top plan view of the slab of FIG. 9;

FIG. 12 is an isometric view of a third pre-cast slab according to the invention;

FIG. 13 is a front plan view of the slab of FIG. 12;

FIG. 14 is a top plan view of the slab of FIG. 12;

FIG. 15 is a cross-sectional view of a portion of the slab of FIG. 12;

FIG. 16 is an enlarged view of a portion of FIG. 14;

FIG. 17 is an enlarged view of a section of the slab of FIG. 9, having additional reinforcing elements;

FIG. 18 is an isometric view of a construction system according to the invention;

FIG. 19 is a top plan view of an expanded implementation of the construction system of FIG. 18.

FIG. 20 is an enhanced isometric view of the construction system in FIG. 18;

FIG. 21 is an isometric view of a further embodiment of the construction system according to the invention;

FIG. 22 is a cut-away view of a floor mounted on a column showing a failure zone due to punching shear;

FIG. 23 is a perspective view of a first frame structure for use in a reinforcing structure of the invention;

FIG. 24 is a perspective view of a second frame structure for use in a reinforcing structure of the invention;

FIG. 25 is a perspective view of a plurality of third frame structures disposed parallel to one another prior to assembly in a reinforcing structure of the invention;

FIG. 26 is a perspective view of an assembly step in assembling a reinforcing structure of the invention, showing the frame structures of FIG. 25 connected together with transverse bottom reinforcing bars;

FIG. 27 is a perspective view of a further assembly step following that of FIG. 26, in which internal transverse reinforcing bars have been added;

FIG. 28 shows the assembly of FIG. 27 from a different perspective view;

FIG. 29 shows the assembly of FIG. 27 in side elevation;

FIG. 30 shows the assembly of FIG. 27 in front elevation;

FIG. 31 shows the assembly of FIG. 27 in a top plan view;

FIG. 32 is a schematic representation of the positioning of the centres of the shear connectors as seen from above in FIG. 31;

FIG. 33 is a perspective view of a further assembly step following that of FIG. 27, in which a first set of extended reinforcing bars have been added which extend beyond the perimeter of the cagework structure; and

FIG. 34 is a perspective view of a further assembly step following that of FIG. 33, in which a second set of extended reinforcing bars, transverse to the first set of extended reinforcing bars, have been added.

The integrated construction system comprises a plurality of different types of pre-cast slabs. With reference to FIGS. 1-3, a pre-cast column slab is indicated generally at 10. The column slab 10 comprises a substantially regular rectangular slab body 12 having a first upper face 12 a and a second lower face 12 b. A through-going aperture 14 is defined at the centre of the slab body 12, the aperture 14 extending from the first upper face 12 a to the second lower face 12 b.

A plurality of rectangular hoops 16 are provided partially set into the slab body 12, a portion of the body of the hoops 16 projecting proud from the upper face 12 a of the slab body 12. With reference to FIGS. 1 and 2, the hoops 16 are provided in a series of spaced-apart rows along the length of the slab body 12.

With reference to FIG. 3, a cross-section of the slab body 12 is shown, taken across the section indicated in FIG. 2. As can be seen in FIG. 3, a first end of each hoop 16 is set within the body of the slab 12. It will be understood that the particular depth that the hoop 16 is set within the slab body 12 is chosen such that the hoop 16 is prevented from being easily detached from the slab body 12, through the application of force to the exposed end of the hoop 16.

A first array of internal reinforcing bars 18 are provided in a parallel arrangement within the slab body 12 along the length of the slab body 12, such that an internal reinforcing bar 18 abuts the inner surface of those corners of the hoop 16 located within the slab body 12. The internal reinforcing bars 18 may be attached to the hoops 16 though any suitable means, e.g. welding.

A second further array of internal reinforcing bars 20 are provided in a parallel arrangement within the slab body 12, the internal bars 20 of the second array lying on top of and transverse to the internal bars 18 of the first array. The internal reinforcing bars 20 of the second array are attached to the internal reinforcing bars 18 of the first array though any suitable means, e.g. welding.

It will be understood that the internal reinforcing bars 18,20 of the first and second arrays do not pass through the defined aperture 14. The first and second arrays of internal reinforcing bars 18,20 provide a lattice of reinforcing members within the slab body 12, the lattice further acting to retain the hoops 16 within position on the slab body 12. The internal lattice outline can be seen in broken-line indication in FIG. 2.

Similarly, turning back to FIG. 1, an external lattice of reinforcing bars is provided external to the slab body 12, the external lattice comprising first and second arrays of external reinforcing bars 19,21. The first and second arrays of external reinforcing bars 19,21 are in line with the first and second arrays of internal reinforcing bars 18,20, and are located at the exposed ends of the hoops 16. The external lattice acts to reinforce the exposed portions of the hoops 16. The external lattice outline is similar to the internal lattice outline shown in FIG. 2.

A set of crosshair reinforcing bars 22 project from the slab body 12 across the width of the defined aperture 14. As can be seen in FIGS. 1 and 2, a first pair of crosshair reinforcing bars 22 a project across the aperture 14 in a first direction, while a second pair of crosshair reinforcing bars 22 b project across the aperture 14 in a second direction at right angles to the first direction. Accordingly, the second pair of crosshair reinforcing bars 22 b abut the top of the first pair of crosshair reinforcing bars 22 a.

While the embodiment shown in the drawings shows an arrangement of four crosshair reinforcing bars 22 a,22 b, it will be understood that other arrangements of reinforcing bars may be employed. It will be understood that the crosshair reinforcing bars 22 a,22 b may be attached to each other though any suitable means, e.g. welding.

With reference to FIG. 3, the side walls of the defined aperture 14 are tapered, such that the aperture 14 extends from a first opening defined at said first upper surface 12 a, to a relatively wider opening defined at said second lower surface 12 b.

The defined aperture 14 and the column reinforcing bars 22 a,22 b are used to couple the column slab 10 to a supporting column, which is now described with reference to FIGS. 4-6.

In general, a multi-level construction project will employ vertical structural columns at various points throughout the structure, the columns often utilising internal reinforcement. With reference to FIGS. 4-6, a structural column is indicated at 30 having a plurality of column bars 32 extending along the length of the column 30. As a building is constructed, the structural columns 30 are built higher as the building advances in height, the columns 30 acting as the primary point of support between successive levels of the building.

In general, as a building is being constructed, when each storey is being installed the structural column 30 initially is built to the level of the new storey (exposing the contained column bars 32), allowing for the reinforcing floor components of the new storey to be interlinked with the column bars 32 of the column. Once the floor of the new storey is complete, the structural column 30 can then be built to the level of the next storey, and the process continues.

When installing the pre-cast column slab 10, the slab 10 is positioned on the structural column 30 such that the exposed column bars 32 project through the defined aperture in the slab 10—FIG. 1. The crosshair reinforcing bars 22 a,22 b can then be secured to the column reinforcing bars 32 through any suitable securing method, interlinking the reinforcement of the column slab 10 with the column 30. The arrangement of the crosshair reinforcing bars 22 a,22 b allows for the relatively easy alignment of the column slab 10 in position on the column 30, as the slab 10 slots into place through the interweaving of the crosshair reinforcing bars 22 a,22 b and the column bars 32.

As the column slab 10 is positioned, other adjacent slabs (indicated as A) are positioned abutting the column slab 10. Suitable adjacent slabs are described in further detail below, as well as a preferred arrangement of slabs. In addition, the slabs may be supported in position during construction using suitable supports (FIG. 6, 38), positioned as required beneath the slabs. Such supports 38 may be removed once construction is completed, and the slabs securely held in place.

Once the arrangement of slabs is complete, and the column slab 10 is in position on the column 30, a further lattice arrangement of reinforcing rods 34 is positioned on top of the external lattice formed by the external reinforcing bars 19,21—FIG. 5. The further lattice 34 comprises an arrangement of transverse and lengthways reinforcing bars configured to be substantially in register with the external lattice and the internal lattice of the slab 10 when positioned on top of the slab 10. The use of the further lattice 34 of reinforcing bars provides further reinforcement of the structure, and ensures that the correct depth of concrete pour will be achieved during installation of the slab 10.

When the further lattice 34 is placed on top of the slab 10, a layer of concrete 36 is then poured onto the slab 10. The concrete 36 is poured such that it fills the defined aperture 14 of the slab 10, and fills the spaces between the first upper face 12 a of the slab 10 and the lattices of bars. The concrete is continued to be poured to reach a particular depth suitable to cover the external portion of the hoops, the external lattice formed by the external reinforcing bars 19,21, and the further lattice arrangement 34.

As the walls of the defined aperture 14 are tapered, as the concrete layer 36 sets, there is a wedge-like interlock between the concrete 36 and the column slab 10, in addition to the anchoring of the external portions of the hoops 16 and the external reinforcing bars 19,21 within the concrete 36. This interlock acts to prevent unwanted movement between the set concrete layer 36, and the underlying column slab 10. This interlock can be seen in more detail in FIG. 7, indicated at B.

Turning to FIG. 8, it can be seen that the column slab 10 is of a greater thickness than that of the adjacent slabs A. This is done to provide for the additional stresses and strains that act upon the column slab 10, requiring greater reinforcement of the column slab 10. While FIG. 8 shows the undersurface of the adjacent slabs A to be in line with the undersurface of the column slab 10, it will be understood that the column slab 10 and the adjacent slabs A may be arranged at other heights relative to one another. Furthermore, it will be understood that the column slab 10 may be dimensioned such that the slab body 12 is stepped or shaped below the level of the other adjacent slabs A, thereby increasing stiffness of the floor with a consequent reduction in deflection.

It will be further understood that the dimensions of the column slab 10, as well as the dimensions of the hoops 16 and the internal and external lattices of reinforcing members, are chosen such that the further lattice 34 of reinforcing bars has the optimum amount of cover of poured concrete 36. The punching shear reinforcement is arranged in such a way to position the three layers of reinforcement for ease of construction and maximisation of floor stiffness.

With reference to FIGS. 9-11, a pre-cast inter-column slab is indicated at 40. The inter-column slab 40 is designed to interlink with the column slab 10 in a preferred embodiment of the invention, but may be employed in any suitable construction scheme. The inter-column slab 40 comprises an elongated rectangular slab body 42, having first and second opposed minor ends 42 a and first and second opposed major ends 42 b.

Within the slab body 42, a plurality of reinforcing bars 44 are arranged in a lattice formation to provide reinforcement of the slab 40. The arrangement of the reinforcing bars 44 can be seen in dashed-line outline in FIG. 11.

A plurality of securing projections 46 are provided at both of the first and second minor ends 42 a of the inter-column slab 40. The securing projections 46 each comprise a pair of rectangular hoops 46, the hoops 48 partially embedded within the slab body 42. The hoops 48 project at an angle from the surface of the slab body 42, such that the exposed ends of the hoops 46 adjoin one another, forming a wedge-shaped securing projection 46 above the surface of the slab body 42. The exposed ends of the hoops 48 are secured to one another using any suitable securing method, forming a rigid wedge-shaped projection. The hoops 46 are positioned such that the ends of the hoops 46 retained within the slab body 42 are interlocked with the reinforcing bars 44 within the slab body 42. The arrangement of interlocking reinforcing elements provides a firm anchor point for securing the inter-column slab 40 with an adjacent slab, e.g. a column slab 10.

While three sets of securing projections 46 are shown at each of the minor ends 42 a of the inter-column slab 40, it will be understood that any configuration of securing projections may be utilised.

With reference to FIGS. 12-14, a pre-cast bridging slab is indicated at 50. The bridging slab 50 is designed to bridge the gap formed between opposed inter-column slabs 40 in a preferred embodiment of the invention (as will be described below), but may be employed in any suitable construction scheme. The bridging slab 50 comprises an elongated rectangular slab body 52, having first and second opposed minor ends 52 a and first and second opposed major ends 52 b.

Within the slab body 52, a plurality of reinforcing bars 54 are arranged in a lattice formation to provide reinforcement of the bridging slab 50. The arrangement of the reinforcing bars 54 can be seen in dashed-line outline in FIG. 14.

The bridging slab 50 further comprises two securing members 56. The securing members 56 are provided partially within the slab body 52, with the respective securing members 56 each located adjacent the respective opposed major ends 52 b of the slab 50, midway along the length of the slab body 52. It will be understood that the securing members 56 are provided closely adjacent the edges of the slab body 52.

The securing members 56 each comprise a pair of adjacent reinforcing bars 58 having a square-wave or crenellated profile (as can be seen in the side view of FIG. 15), the bars 58 arranged along a portion of the length of the slab body 52, parallel to the adjacent major end 52 b of the slab body 52. The securing members 56 are arranged such that a lower portion of the reinforcing bars 58 is provided within the slab body 52, with an upper portion of the crenellated reinforcing bars 58 projecting proud of the surface of the slab body 52. The upper portion of the crenellated reinforcing bars 58 project at an angle from the surface of the slab body 52, such that the uppermost portion of the adjacent crenellated bars 58 adjoin one another, and are secured to one another at this point. The crenellated reinforcing bars 58 thus form the crenellated wedge-shaped structure of the securing member 56.

The lower portions of the securing members 56 are positioned within the slab body 52 such that the reinforcing bars 58 of the members 56 interlock and can be secured to the lattice of reinforcing bars 54 provided within the slab body 52 (see FIG. 15). Furthermore, and with reference to the enlarged view of FIG. 16, a series of U-shaped reinforcing bars (or braces) 60 are provided within the slab body 52 in the region of the securing members 56.

As can be seen from FIG. 16, the U-shaped bars 60 are arranged such that the free ends of the bars 60 project across the centre line of the securing members 56. It will be understood that the U-shaped bars 60 are provided at a shallower depth within the slab body 52 than the depth of the lower portions of the securing members 56, such that the U-shaped bars 60 act as a further reinforcement of the securing members 56 within the slab body 52. The use of the U-shaped reinforcing bars 60 acts to further distribute the stresses and strains acting on the securing members 56 within the slab body 52.

From the accompanying drawings, it can be seen that the securing projections 46 of the inter-column slab 40 as well as the securing members 56 of the bridging slab 50 are provided such that they aligned to extend along the longitudinal direction of the slabs in which they are located. For a regular grid-link arrangement of the network of reinforcing bars, this ensures that lateral bars of the network of reinforcing bars engage with the securing projections and members at right angles, securely aligning the securing projections and members in parallel with the longitudinal bars of the reinforcing network. As the longitudinal bars of the reinforcing network provide the majority of the structural stiffness within the slabs, this arrangement provides for the optimum distribution of the components of the slabs to ensure optimum reinforcement.

It will be understood that the components of the inter-column slab 40 and the bridging slab 50 as shown in the accompanying drawings may further implemented in other slabs. For example, the bridging slab 50 may further comprise corresponding securing projections 46, as illustrated in FIGS. 9-11, in addition to securing members 56. Conversely, the inter-column slabs 40 may further utilise corresponding securing members 56, as shown in FIGS. 12-14.

It will be understood that the slabs 10, 40, 50 may be utilised in any suitable construction system, providing a balance between adequate reinforcement and efficient use of material resources, as reinforcement is concentrated at those locations most likely to undergo additional stresses and strains, e.g. at the structural support columns, the interface between adjacent pre-cast slabs, etc. In addition, further enhancements may be made to the described components to provide additional reinforcement. For example, FIG. 17 shows a portion of an inter-column slab 40, wherein additional reinforcing members 62 have been provided extending between the exposed corners of hoops 48. Such additional reinforcing members 62 provide extra reinforcement, as well as enhancing the flexibility of use of the slab 40 by providing additional fixation points that components can be anchored to.

The slabs 10, 40, 50 may be utilised in a preferred construction system, as illustrated in FIGS. 18 and 19, which aims to maximise the reinforcement features of the slab designs. In the preferred system, column slabs 10 are positioned on the structural columns projecting from the preceding level (as described above). Inter-column slabs 40 are positioned between adjacent column slabs 10, forming a network provided by the arrangement of the inter-column slabs 40, having column slabs 10 located at the interface between orthogonal inter-column slabs 40. As will be seen in FIG. 18, the column slabs 10 are generally of a greater depth than the surrounding inter-column slabs 40. This is done to ensure that the column slabs 10 have the greater structural strength required when in a position of relatively high stresses and strains.

Bridging slabs 50 are then positioned such that they extend between pairs of opposed inter-column slabs 40, as shown in FIG. 18. The final spaces between the parallel inter-column slabs 40 and the bridging slab 50 can be filled using any standard pre-cast concrete slabs 70 of suitable dimensions.

Once the slabs 10, 40, 50, 70 are positioned, any suitable further reinforcing bars may be introduced to the construction, anchored to the various securing fixtures (i.e. the exposed hoops 16 and the external lattice of the column slabs 10; the securing projections 46 of the inter-column slabs 40; and the securing members 56 of the bridging slabs 50). Further lattices or layers of bars may be introduced as appropriate, and as described above, the layer of concrete is then poured over the slabs and the additional reinforcing elements which, when set, completes the construction of the present layer. As described above, the three-layer arrangement of networks of reinforcing bars at the column slabs 10 provide increased punching shear reinforcement at the interface between a floor and the supporting column.

The structural columns may then be advanced to the height of the next layer, and the procedure repeated as appropriate. As will be understood, the particular layout pattern of slabs may be reproduced as appropriate throughout the present layer—for example, the layout shown in FIG. 19 is an expansion of the individual pattern component shown in FIG. 18.

The use of this layout system involving this patterning, comprising the slabs as described herein, provides for a standardisation of a relatively easily reproducible design, which can be implemented on a construction site without requiring extensive training. Also, as the reinforcing elements are concentrated at those points of the construction subject to the most stresses and strains, there is a more efficient use of reinforcing materials in the construction, therefore bringing down the overall cost of construction.

Another advantage of the concentration of the reinforcing elements between the different slabs is that, as certain slabs will be subjected to additional stresses and strains (and consequently have more reinforcement per unit area—e.g. a column slab 10 as opposed to a standard pre-cast concrete slab 70), then such slabs may undergo more rigorous stress testing procedures to ensure the integrity of the eventual construction. As such tests can be tailored to the individual components, the confidence of the results of these tests can be improved, as well as the confidence in the performance of the overall construction.

The slabs described are also suitable for efficient transportation and storage, as the external reinforcement elements provide for vertical stacking of the slabs prior to use.

It will be understood that any of the slabs used may be of varied dimensions in order to accommodate the different building requirements. It will also be understood that the shape of the slabs may be adapted as appropriate subject to requirements, for example decorative mouldings may be provided on the underside of the slabs for aesthetic purposes.

With reference to FIG. 20, an embodiment of the construction system of FIG. 18 is shown, with the structural columns 30 and the column bars 32 clearly illustrated. For clarity, the arrangement of exposed reinforcement members is shown on only one of the column slabs 10 a, and the crosshair arrangement of the reinforcing bars provided in the aperture of a column slab is shown on one of the other column slabs 10 b. Furthermore, the inter-column slabs 40 and the bridging slabs 50 are shown as having both securing projections 46 and securing members 56, as described above. In addition, the slabs 70 between parallel inter-column slabs 40 and bridging slabs 50 are shown as having both securing projections 46 and securing members 56 to improve stability of construction.

With reference to FIG. 21, a further embodiment of the system shown in FIG. 20 is illustrated. Here, it should be noted that the upper surfaces of the column slabs 10 and the inter-column slabs 40 are at the same level and in register with one another. The bridging slab 50 and the slabs 70 can be seen to rest on the edges of the upper surfaces of the column slabs 10 and the inter-column slabs 40, providing additional support to the bridging slab 50 and slabs 70. In this embodiment, it will be understood that the dimensions of slabs used as well as that of the securing projections 46 and securing members 56 can be varied to accommodate securing between adjacent slabs.

The reinforcement can also be provided as a stand-alone construction of reinforcing bars made, for example of steel or another structural material which provides sufficient reinforcement to a floor. Such a reinforcing structure need not be provided in pre-case slabs but can also be provided as a cagework structure which is pre-assembled and positioned on top of a column, or which can be assembled in situ from a number of pre-assembled frame structures.

FIG. 23 shows an example of a frame structure, having a first reinforcement bar 86 of 20-25 mm diameter steel reinforcement and a second reinforcement bar 88 of 12-16 mm diameter steel. It is important that the first and second (i.e. top and bottom respectively) steel reinforcement bars used in such a frame structure are of a grade suitable to provide top layer and bottom layer reinforcement to a floor, i.e. they will be an integral part of the floor reinforcement.

A plurality of shear connectors 90, in the form of elongated, sausage shaped hoops, are connected to and contain the first and second reinforcing bars 86,88. The frame structure is thus a rigid, welded structure which includes elements intended to form part of the top layer steel, the bottom layer steel, and the shear reinforcement of a floor. The shear reinforcement 90 is thus rigidly connected to and contains the top and bottom reinforcement steel 86,88.

A second example of frame structure, in the form of a elongated trapezoidal cuboid frame is shown in FIG. 24. This frame structure has a pair of first (top) reinforcing bars 92, a pair of second (bottom) reinforcing bars 94, and a plurality of trapezoidal hoops 96, each in the form of a parallelogram, with the first and second reinforcing bars being each welded to a respective internal corner of each hoop, whereby the hoops 94 provide shear reinforcement between the top and bottom reinforcement members when incorporated within the reinforcing steelwork of a floor.

The assembly of a reinforcing cagework structure will now be described based on a third and presently preferred example of frame structure 100 a-100 g, seven of which are shown disposed in parallel arrangement in FIG. 25 prior to assembly into a cagework structure. The structure can be assembled offsite or the frame structures 100 a-100 g of FIG. 25 can be assembled together into a reinforcing cagework structure on site, i.e. at the head of a column.

Taking frame structure 100 a as an example, each frame structure has a pair of first (top) reinforcing bars 102 and a pair of second (bottom) reinforcing bars 104, each connected to a respective internal corner of a plurality of hoop-like rectangular shear connectors 106 distributed along the length of the frame structure. The rectangular hoop-like shear connectors are manufactured from a single length of reinforcing steel formed into a rectangle with overlapping ends 107 disposed at the top side of the frame structure. Thus each frame structure 100 a-100 g forms a rigid, preassembled structure in which elements of top layer reinforcement and bottom layer reinforcement for a floor are integrated and connected to shear reinforcement members 106.

The distribution of shear connectors is not uniform along the different frame structures 100 a-100 g, as will become clear later. It can also be seen that the spatial separation between adjacent structures 100 a and 100 b or adjacent structures 100 f and 100 g is somewhat greater than the separation between each other adjacent pair of structures such as 100 b and 100 c, again for reasons described below.

The next step of assembly is shown in FIG. 26, which also shows the differential spatial separation between the endmost pairs of adjacent structures 100 a,100 b and 100 f,100 g when compared with the internal pairs 100 b,100 c; 100 c,100 d; 100 d,100 e; and 100 e,100 f.

The next assembly step is shown in FIG. 26, in which a set of bottom transverse internal bars 108 have been laid across and welded to the second (bottom) reinforcing bars 104. Using the conventional notation for identifying the layers of steel reinforcement in a structure such as a floor, in which the bottom layers are numbered B1, B2, etc from the outermost inwards, the second reinforcing bars 104 form layer B1 and the bottom transverse internal bars added in FIG. 26 will form layer B2 when the structure is set into a floor. As will become apparent as more steel is added in later Figures, the first (top) reinforcing bars 102 of the frame structures 100 a-100 g will form a part of the T2 layer, i.e. the layer of horizontal steel reinforcement positioned secondmost from the top of the floor surface.

In FIG. 27, the T3 layer is added, namely a set of top transverse internal bars 110 positioned immediately underneath and welded to the first reinforcing bars 102 and disposed parallel to the bottom transverse internal bars 108 and thus also parallel to the plane of the rectangular shear connectors 106 and perpendicular to the direction of the first and second reinforcing bars 102,104.

FIG. 28 shows the same structure as FIG. 27 in a different perspective view taken from above, in front and the left side.

FIG. 29 shows the same structure as FIG. 27 in a left side elevation, in which one can particularly see the structure of the rectangular hoop-like shear connectors with overlapping ends 107.

FIG. 30 shows the same structure as FIG. 27 in a front elevation.

FIG. 31 shows the same structure in a top plan view, which again shows the overlapping ends of hoop-like shear connectors 106. In FIG. 31, due to the greater diameter of the first reinforcing bars 102 compared to the second reinforcing bars 104, and the fact that the latter are positioned directly underneath the former, the latter are hidden from view. Similarly, due to the greater diameter of the top transverse internal reinforcing bars 110 compared to the bottom transverse reinforcing bars 108, and the fact that the latter are positioned directly underneath the former, the latter are hidden from view. Thus, the majority of the tensile strength of the structure of FIGS. 27-31 is concentrated in the top layers 102,110. In FIG. 31, reference numeral 112 denotes the notional centre point of the structure, located in the square gap formed between the centremost pair of first reinforcement bars and the centremost pair of top transverse internal reinforcement bars. As will be apparent from the earlier embodiments, these bars form the crosshair bars to which the vertical reinforcement of a column are connected when the cagework structure is placed over a column. (Unlike earlier embodiments, the crosshair bars form part of the overall reinforcement of the cage in this embodiment, being continuous with and part of the main top and bottom reinforcement steel.)

FIG. 32 is a schematic representation of the positioning of the centres of the shear connectors as seen from above in FIG. 31. Each small circle 106 (a few of which are denoted) represents the position of the centre of a shear connector relative to the centre point 112 of the cagework structure illustrated in FIG. 31. The grid lines 114 shown in FIG. 32 are notional only to give a representation of the relative spacing between shear connectors 106, and these grid lines and their spacing bear no relationship to the various reinforcing bars 102,104, 108, 100 of the cage structure seen in previous figures.

Three notional circles are shown in FIG. 32, namely an inner circle 116, a middle circle 118 and an outer circle 120. These circles again bear no relationship to actual structural elements of the cagework structure but rather represent three zones of reinforcement. The number and size of shear connectors in each zone can be varied to meet the requirements of the Codes of practice.

FIG. 33 shows the further assembly of the reinforcing structure, in which the central cagework is supplemented by a first set of extended reinforcing bars 122 which extend beyond the perimeter of the cagework structure as defined by the original frame members 100 a-100 g shown in FIG. 25. As best seen along the top left edge 124 of the structure, each bar of the first set of extended reinforcing bars 122 is positioned against the external top corner of a row of shear connectors 106, sandwiching that corner between itself 122 and the first reinforcing bar 102 at the internal angle of that corner. Thus the first set of extended reinforcing bars 122 are co-planar with the first reinforcing bars of the frame structures 100 a-100 g (FIG. 25) and lie on top of (and are connected to) the top transverse internal reinforcing bars 110. As such the first set of extended reinforcing bars 122, along with the first reinforcing bars 102, form part of the T2 layer of reinforcing steel.

FIG. 34 shows the structure after a further assembly stage, where a second set of extended reinforcing bars 126, transverse the first set 122, has been laid on top of the first set of extended reinforcing bars 122 and the first reinforcing bars 102 of the frame structure and welded thereto. The second set of reinforcing bars 126 thus forms layer T1 of the floor, being the uppermost layer.

Together the first and second sets of extended reinforcing bars extend the main floor steel reinforcement outwards beyond the cagework, allowing the remaining floor reinforcement to be integrated with the cagework structure.

The cagework reinforcing structure can be pre-assembled offsite, either with or without the extended reinforcing bars 122,126, or it can be assembled onsite from the individual frame structures 100 a-100 g. The structure can also be embedded offsite into a slab with at least the bottom reinforcing bars and the lower part of the shear connectors embedded in the concrete, thereby providing a pre-cast column slab similar to that of FIG. 1 to be used in a similar manner, with extended reinforcing bars added onsite for connection to inter-column slabs etc. The invention is not limited to the embodiments described herein but can be amended or modified without departing from the scope of the present invention. 

1. A reinforcing structure for use in supporting a floor at a junction thereof with a structural column, comprising: a plurality of generally elongate, preassembled frame structures, each frame structure having a major longitudinal axis, said frame structures being disposed in rows with their major longitudinal axes parallel to one another, and each frame structure comprising: at least one first reinforcing bar disposed parallel to the major longitudinal axis of said frame structure; at least one second reinforcing bar disposed parallel to the major longitudinal axis of said frame structure; a plurality of shear connectors disposed at spaced intervals along the longitudinal axis of the frame structure, each shear connector comprising a reinforcing member extending between a first reinforcing bar and a second reinforcing bar, the reinforcing member being shaped to extend around the first and second reinforcing bars such that they are tied together by the reinforcing member; a plurality of transverse internal reinforcing bars disposed parallel to one another and connected across the first or second reinforcing bars of each frame structure to connect the preassembled frame structures into a cagework of spaced-apart, rigidly connected frame structures.
 2. A reinforcing structure as claimed in claim 1, wherein the reinforcing member comprises a top portion, a bottom portion, and a bridging portion between the top and bottom portions, the bridging portion extending between the first and second reinforcing bars, and the top and bottom portions each extending in a direction transverse to the first and second reinforcing bars to contain the first and second reinforcing bars.
 3. A reinforcing structure as claimed in claim 2, wherein the bridging portion and at least a part of the top and bottom portions together define an elongated C shaped section of the shear connector.
 4. A reinforcing structure as claimed in claim 2, wherein the shear connector is in the form of a hoop which includes a pair of said bridging portions, said top portion and said bottom portion.
 5. A reinforcing structure as claimed in claim 1, wherein at least one first reinforcing bar comprises a first pair of reinforcing bars disposed parallel to one another and to said major longitudinal axis, and spaced apart from one another along the direction of the transverse internal reinforcing bars to provide a pair of top edges of the frame structure.
 6. A reinforcing structure as claimed in claim 1, wherein said at least one second reinforcing bar comprises a second pair of reinforcing bars disposed parallel to one another and to said major longitudinal axis, and spaced apart from one another along the direction of the transverse internal reinforcing bars to provide a pair of bottom edges of the frame structure.
 7. A reinforcing structure as claimed in claim 6, wherein at least one first reinforcing bar comprises a first pair of reinforcing bars disposed parallel to one another and to said major longitudinal axis, and spaced apart from one another along the direction of the transverse internal reinforcing bars to provide a pair of top edges of the frame structure, and wherein each shear connector comprises a generally rectangular hoop having four interior corners with a respective one of each of said first and second pairs of reinforcing bars connected to the hoop at a respective interior corner thereof.
 8. A reinforcing structure as claimed in claim 1, wherein said shear connectors are spaced along each frame structure such that their two dimensional arrangement across said cagework provides a zone of shear reinforcement, whereby when said reinforcing structure is mounted on a structural column to support a reinforced floor, said zone of shear reinforcement coincides with the region in which maximum punching shear is experienced between the column and the floor.
 9. A reinforcing structure as claimed in claim 1, comprising two sets of said transverse internal reinforcing bars, namely a set of top transverse internal reinforcing bars connected to the underside of the first reinforcing bars and a set of bottom transverse internal reinforcing bars connected to the top side of the second reinforcing bars, whereby the first reinforcing bars are sandwiched between the top transverse internal reinforcing bars and a top portion of the shear connectors and the second reinforcing bars are sandwiched between the bottom transverse internal reinforcing bars and a bottom portion of the shear connectors,
 10. A reinforcing structure as claimed in claim 1 further comprising a first set of extended reinforcing bars which extend horizontally beyond the perimeter of said cagework as defined by the frame structures, the first set of extended reinforcing bars disposed in a direction parallel to the first reinforcing bars of the frame structures.
 11. A reinforcing structure as claimed in claim 7, wherein said shear connectors are spaced along each frame structure such that their two dimensional arrangement across said cagework provides a zone of shear reinforcement, whereby when said reinforcing structure is mounted on a structural column to support a reinforced floor, said zone of shear reinforcement coincides with the region in which maximum punching shear is experienced between the column and the floor and wherein the first set of extended reinforcing bars are disposed on top of the top transverse internal reinforcing bars in the plane of the first reinforcing bars.
 12. A reinforcing structure as claimed in claim 10, wherein said first set of extended reinforcing bars are connected to the outside of the shear connectors such that the shear connectors are sandwiched between the first reinforcing bars and the first set of extended reinforcing bars.
 13. A reinforcing structure as claimed in claim 1 further comprising a second set of extended reinforcing bars which extend horizontally beyond the perimeter of said cagework as defined by the frame structures, the second set of extended reinforcing bars disposed in a direction parallel to the transverse internal reinforcing bars.
 14. A reinforcing structure as claimed in claim 13, wherein the second set of extended reinforcing bars are disposed on top of the first reinforcing bars of the frame structures.
 15. A reinforcing structure as claimed in claim 13, comprising two sets of said transverse internal reinforcing bars, namely a set of top transverse internal reinforcing bars connected to the underside of the first reinforcing bars and a set of bottom transverse internal reinforcing bars connected to the top side of the second reinforcing bars, whereby the first reinforcing bars are sandwiched between the top transverse internal reinforcing bars and a top portion of the shear connectors and the second reinforcing bars are sandwiched between the bottom transverse internal reinforcing bars and a bottom portion of the shear connectors, wherein one or more of the top transverse internal reinforcing bars coincide with one or more of the second set of internal reinforcing bars when viewed from above the reinforcing structure.
 16. A method of constructing a reinforced floor, comprising the steps of: (i) providing a reinforcing structure for use in supporting a floor at a junction thereof with a structural column, said reinforcing structure comprising: a plurality of generally elongated, preassembled frame structures, each frame structure having a major longitudinal axis, said frame structures being disposed in rows with their major longitudinal axes parallel to one another, and each frame structure comprising: at least one first reinforcing bar disposed parallel to the major longitudinal axis of said frame structure; at least one second reinforcing bar disposed parallel to the major longitudinal axis of said frame structure; and a plurality of shear connectors disposed at spaced intervals along the longitudinal axis of the frame structure, each shear connector comprising a reinforcing member extending between a first reinforcing bar and a second reinforcing bar, the reinforcing member being shaped to extend around the first and second reinforcing bars such that they are tied together by the reinforcing member; and a plurality of transverse internal reinforcing bars disposed parallel to one another and connected across the first or second reinforcing bars of each frame structure to connect the preassembled frame structures into a cagework of spaced-apart, rigidly connected frame structures; (ii) mounting said reinforcing structure on a structural support column such that the cagework sits horizontally; (iii) providing extended reinforcing bars which extend horizontally beyond the perimeter of said cagework as defined by the frame structures; and (iv) pouring a solidifying structural substance in a layer which captures said reinforcing structure, whereby said solidifying structural substance solidifies to form a reinforced floor.
 17. A method as claimed in claim 16, wherein the step of providing a reinforcing structure comprises providing said plurality of frame structures and said plurality of transverse top reinforcing bars, and constructing said reinforcing structure in situ on said column by connecting said frame structures and said reinforcing bars to one another and to said column to provide said cagework.
 18. A method as claimed in claim 17, wherein the step of providing a reinforcing structure comprises providing said reinforcing structure as a pre-assembled cagework, and mounting said cagework to said column.
 19. A method of constructing a reinforced floor, comprising the steps of: (i) providing a reinforcing structure for use in supporting a floor at a junction thereof with a structural column, said reinforcing structure comprising: a plurality of generally elongated, preassembled frame structures, each frame structure having a major longitudinal axis, said frame structures being disposed in rows with their major longitudinal axes parallel to one another, and each frame structure comprising: at least one first reinforcing bar disposed parallel to the major longitudinal axis of said frame structure; at least one second reinforcing bar disposed parallel to the major longitudinal axis of said frame structure; and a plurality of shear connectors disposed at spaced intervals along the longitudinal axis of the frame structure, each shear connector comprising a reinforcing member extending between a first reinforcing bar and a second reinforcing bar, the reinforcing member being shaped to extend around the first and second reinforcing bars such that they are tied together by the reinforcing member; and a plurality of transverse internal reinforcing bars disposed parallel to one another and connected across the first or second reinforcing bars of each frame structure to connect the preassembled frame structures into a cagework of spaced-apart, rigidly connected frame structures; (ii) pouring a solidifying structural substance in a layer which captures said reinforcing structure, whereby said solidifying structural substance solidifies to form a reinforced floor slab; (iii) mounting said reinforced floor slab on a structural support column such that the cagework sits horizontally; and (iv) building a reinforced floor outwardly from said mounted reinforced floor slab either by pouring a floor around reinforcing bars extending from said reinforced floor slab or by connecting additional floor slabs to said mounted reinforced floor slab.
 20. A method as claimed in claim 19, wherein the step of pouring a solidifying structural substance in a layer results in said layer having a depth which captures the bottom edges and a portion of the shear connectors of each frame structure, leaving the top edges exposed, whereby extended reinforcing bars may be mounted to the exposed top portions of the frame structures to provide extended reinforcement to the floor beyond the floor slab.
 21. A reinforced floor comprising a reinforcing structure according to claim 1, mounted on a structural support column, and having extended reinforcing bars extending therefrom beyond the perimeter of said cagework as defined by the frame structures, and further comprising a solid structural material in a layer which surrounds and contains said reinforcing structure and said extended reinforcing bars.
 22. A reinforced floor according to claim 21, wherein said structural material is concrete.
 23. A pre-cast column slab for use in a pre-cast construction system, the slab comprising: a main body having an upper surface and a lower surface; a first network of reinforcing bars disposed within said main body; a plurality of discrete hoop elements, the hoop elements in the form of a closed loop, said hoop elements disposed partly within said main body and partly projecting above the upper surface of said main body, such that one or more of said first network of reinforcing bars pass through said hoop elements; and a second network of reinforcing bars located above said upper surface of said main body, such that one or more of said second network of reinforcing bars pass through said hoop elements.
 24. The column slab of claim 23, wherein said hoop elements are provided in said column slab in a regular grid arrangement of spaced parallel rows of hoop elements.
 25. A pre-cast utility slab for use in a pre-cast construction system, the slab comprising: a substantially rectangular main body having an upper surface and a lower surface, the main body further having a pair of opposed major ends and a pair of opposed minor ends; a network of reinforcing bars disposed within said main body; and at least one coupling member comprising a reinforcing frame having a crenellated side profile, wherein a lower portion of said reinforcing frame is provided within said main body and an upper portion of said reinforcing frame projects above the upper surface of said main body, and wherein said coupling member is interlaced with said network of reinforcing bars.
 26. A construction system comprising a plurality of pre-cast column slabs as claimed in claim 23, a first plurality of pre-cast utility slabs comprising: a substantially rectangular first main body having a first upper surface and a first lower surface, the first main body further having a pair of first opposed major ends and a pair of first opposed minor ends; a first network of reinforcing bars disposed within said first main body; and at least one first coupling member comprising a first reinforcing frame having a first crenellated side profile, wherein a first lower portion of said first reinforcing frame is provided within said first main body and a first upper portion of said first reinforcing frame projects above the first upper surface of said first main body, and wherein said first coupling member is interlaced with said first network of reinforcing bars; and a second plurality of pre-case utility slabs comprising: a substantially rectangular second main body having a second upper surface and a second lower surface, the second main body further having a pair of second opposed major ends and a pair of second opposed minor ends a second network of reinforcing bars disposed within said second main body; and at least one second coupling member comprising a second reinforcing frame having a second crenellated side profile, wherein a second lower portion of said second reinforcing frame is provided within said second main body and a second upper portion of said second reinforcing frame projects above the second upper surface of said second main body, and wherein said second coupling member is interlaced with said second network of reinforcing bars; and wherein said column slabs are arranged in a spaced-apart grid arrangement, a first plurality of said utility slabs are arranged such that the first plurality of said utility slabs extend between opposed column slabs, and at least one of a second plurality of utility slabs is arranged such that the at least one of said second plurality of bridging slabs extends between an opposed pair of said first plurality of utility slabs. 